The present invention relates generally to a new apparatus and method for in-situ green sheet slitting. More particularly, the invention encompasses an apparatus and method that uses a modified green sheet slitting machine so that it can provide an in-situ slitting of green sheets that result in a plurality of separate green sheets rolls or strips.
The invention is directed more to the slitting or indenting of the ceramic green sheet to any desired dimensions without the need of costly special tooling. The invention also solves the problem of building customized doctor blades to precise specifications and design. The inventive mechanism slits the green sheet tape by indenting the uncured ceramic tape with specially designed wheels. The invention uses the wheel""s xe2x80x9ctoe-inxe2x80x9d effect to part the uncured tape to its desired size. The slitting mechanism itself is located inside the curing oven and the slitting or indenting of the ceramic green sheet is done during the curing process and not after the curing process.
Ceramic substrates for electronic applications are becoming more dense with the evolution of new technology. However, increases in circuit density produce a corresponding increase in overall manufacturing problems. Ceramic substrates manufacturers are therefore constantly challenged to improve the quality of their products by identifying and eliminating problems which produce defective parts. Whereas significant improvements are being made to eliminate systematic defects by reducing process variability. Process improvements alone are not sufficient to eliminate all the random defects which effect both yield and reliability. Historically, screening techniques have been employed to improve product failure rates to acceptable levels by culling out many of these random defects.
Normally, these ceramic substrates are made by using casting slurry or ceramic slip of material contained in a hopper. The slip material is typically a mixture of ceramic powder, organic binder and solvents. The ceramic tape or the green sheet is formed with the extrusion of a film of slurry on to a supporting or carrier strip or sheet, using a method known in the art as doctor blading. The ceramic slurry which is on the upper surface of the supporting strip is processed through a conventional belt type oven and the cured ceramic sheet along with the backing or carrier material is then spooled onto a spool. The conventional method of slitting the ceramic sheet is to cut through the cured ceramic tape forming individual blanks or green sheets. This conventional cutting process produces ceramic debris because this cutting is done to the solid cured ceramic sheet, which also creates contamination. The debris from the ceramic also creates other problems, such as, for example, defective parts, cleaning of the equipment, etc., and this of course adds cost to the process.
U.S. Pat. No. 1,998,357 (Carlson) discloses a web cutting and scoring device. A web of sheet material is brought in contact with a plurality of cutter knives and rotary scoring blades to create tracks, in order to either cut or score the web of sheet material into strips. A backing roller also helps provide the necessary pressure in the scoring or cutting operation of the web of sheet material.
U.S. Pat. No. 4,570,518 (Burmeister) discloses an apparatus for slitting of continuous webs into ribbons. The web material passes between a plurality of cutting blades and a backing roller and are cut into individual ribbons.
U.S. Pat. No. 5,051,219 (Miller) discloses an automatic handling of green ceramic tapes. A green ceramic tape on a supporting strip is rolled off a flanged roller. The supporting strip is then separated from the green ceramic tape and is wound-up on a spool for possible reuse, while the green ceramic tape is processed through a blanking press to form a plurality of blanking cards.
The above-mentioned problems of the prior art have been solved by the method and apparatus of this invention where the green sheet is unconventionally indented during the initial stages of the curing process and the curing process automatically divides the indented ceramic sheet into tapes or ribbons during the curing stage and these tapes or ribbons are free of any cutting contamination.
The invention is a novel method and an apparatus for in-situ green sheet slitting.
Therefore, one purpose of this invention is to provide an apparatus and a method that will provide an in-situ green sheet slitting.
Another purpose of this invention is to provide for a cutting wheel that will slit the green sheet without cutting or puncturing or penetrating the carrier or supporting sheet.
Still another purpose of this invention is to have a wheel that is toed-in at an angle to preclude the possible fusion of the ceramic tape or material.
Yet another purpose of this invention is to provide an indenting apparatus that can be located inside an oven or a heating chamber.
Still yet another purpose of the invention is to provide a ceramic tape or spool that is free from cutting debris.
Yet another purpose of this invention is to provide an indenting apparatus that will indent a continuous green sheet material inside an oven.
Therefore, in one aspect this invention comprises an apparatus for slitting ceramic green sheets comprising,
(a) a slitting mechanism having at least one slitting wheel,
(b) moving means for bringing at least one layer of ceramic green sheet underneath said at least one slitting wheel, and wherein at least a portion of said at least one layer of ceramic green sheet is slit by said at least one slitting wheel.
In another aspect this invention comprises a method for slitting ceramic green sheets comprising,
(a) a slitting mechanism having at least one slitting wheel,
(b) wherein at least one layer of ceramic green sheet is brought underneath said at least one slitting wheel, and wherein at least a portion of said at least one layer of ceramic green sheet is slit by said at least one slitting wheel.
In yet another aspect this invention comprises a method for slitting ceramic green sheets comprising,
(a) contacting at least one green sheet with at least one slitting wheel prior to the time said green sheet has been cured, and
(b) fully curing said green sheet, and wherein said slit widens and causes a separation in said green sheet.